N.Y.C. Legionnaires’ Outbreak Over, City Says

New York City’s Legionnaires’ disease outbreak is officially over, health officials said on Thursday, confirming that the Opera House Hotel in the South Bronx was its source.

The outbreak, which officials called the worst for Legionnaires’ in the city’s history, killed 12 people and sickened 128 since early July. No new illnesses have been identified since Aug. 3, longer than the disease’s two-week incubation period.

“Today, I’m happy to declare that the outbreak is over,” Health Commissioner Mary Bassett said at a news conference on Thursday. Ninety-four percent of those hospitalized have been discharged, she said.

The “DNA fingerprint” of the bacteria found in the boutique hotel’s cooling tower matches that found in patients, officials said. City officials obtained 25 samples from such patients, some of whom had died, Dr. Bassett said. “What our data suggests is that the Opera House was releasing contaminated water mist,” she said.

In July, city officials identified five cooling towers, the industrial air-conditioning structures atop large buildings, as likely sources of the outbreak. City and state teams eventually identified 20 cooling towers in the Bronx that carried Legionella, the bacteria that causes the pneumonia-like disease.

“This mist can spread under certain conditions for a long distance,” said Dr. Jay Varma, deputy commissioner for disease control, at Thursday’s news conference. “It can be even more than a mile, potentially.” The city mobilized “an army of disease detectives” to determine the source of the disease through testing and interviews, Dr. Varma said. Their findings pointed to the hotel. “There really was a very large clustering of cases within a one-mile radius around this place that would not be expected by chance.”

Andy Tse and Elizabeth Ferreras take a water sample from a cooling tower on the roof of Montefiore Medical Center in the Bronx in early August. Photo: Philip Kamrass/Office of Governor Andrew M. Cuomo

Samples of the bacteria were tested at three labs.There are different strains of Legionella, according to the Health Department. “We now know that for every one of the samples for which testing is now complete, there is a match with the strain found at the Opera House Hotel,” Dr. Bassett said.

None of the strains found at other cooling towers matches that found in patients associated with the outbreak, Dr. Bassett said. Other towers that tested positive were atop a high school, post office, nursing home, hospital and other buildings.

“The people who became infected and developed Legionnaires’ disease breathed it in from a contaminated mist that was released in the neighborhood,” Dr. Bassett said.

Opera House Hotel spokesman Michael McKeon issued a statement calling the news “disappointing,” saying that the hotel’s two-year-old system “has the most up-to-date technology available and our maintenance plan has been consistent with the regulations that both the city and the state are putting in place.”

The hotel will go beyond the new regulations and test its cooling tower every 30 days, when the tower is in operation, he said.

At the news conference, Dr. Bassett called the hotel “extraordinarily cooperative,” although she said the levels of disinfectant in its cooling tower had been low.

The conditions in a cooling tower can shift quickly, she said: “Maintenance plays a role, but the circumstances that allow bacteria to grow can change rapidly.”

In light of the outbreak, both the city and state implemented new regulations for the cleaning and maintenance of cooling towers. The city’s law, signed by Mayor Bill de Blasio on Tuesday, requires registration, annual certification, quarterly inspection and reporting to the city’s health department of increased microbes in cooling towers.

Those who violate the law are liable for penalties up to $10,000, and failure to disinfect towers that have elevated bacteria levels is now a misdemeanor, with fines up to $25,000.

Dr. Bassett said that while this outbreak is over, people may still contract the disease. “Legionella bacteria are ubiquitous in our environment and we will continue to see cases, though I hope we will never again see cases on this scale,” she said.The city typically gets 200 to 300 cases a year, she said.